However, from the latest info I have read, toe is better when kept constant throughout the suspension travel. Toe changes can make the car's behaviour less predictable. This is contrary to my original intuition, so will try to dig some more .

Yes, of course less slop in suspension is better but most of us have to compromise. I think BMW engineered a very livable compromise for dual duty cars. You see in other threads, I've wrongly assumed that the rear suspension design of an E9X M3 acts in a similar manner to the E46 (non-M and M) which was pretty much the same as the E36. I know my E46 very well so I can and do maintain input on how the car is setup...just not relying on someone's opinion. I know all of us know the what, what the spec should be. I think all of us would be better served if we knew why the spec is what it is...I surely don't right now.

In the end I know that being intimately familiar with most of the details on my E46 has made me a better driver.